In a communication system, data is communicated between a sending station and a receiving station by way of a communication channel. The communication channel connects the sending station together with the receiving station. Data, to be communicated by the sending station to the receiving station, is converted into a form to permit its communication upon the communication channel. And, once delivered at the receiving station, the informational content of the data is recovered.
As a result of advancements in communication technologies, many different types of communication systems have been developed, and implemented. And, many different types of communication services are implementable through use of several of the different types of communication systems.
A radio communication system is an exemplary type of communication system. Various radio communication systems permitting various types of communication services to be effectuated therethrough have been developed and implemented.
In a radio communication system, the communication channel that interconnects the sending and receiving stations of the communication system is defined upon a radio link extending between the sending and receiving stations. The radio link is defined upon a portion of the electromagnetic spectrum. Inherent mobility is provided in a radio communication system as the radio link, rather than a conventional wireline connection interconnects the sending and receiving stations. In contrast, a communication system requiring use of conventional wireline connections by which to interconnect sending and receiving stations is generally of limited mobility due to the need to interconnect the sending and receiving stations by the wireline connection.
A cellular communication system is a type of radio communication system that has achieved significant levels of usage in recent years. The networks of various types of cellular communication systems have been installed throughout significant areas of the populated portions of the world. Communications effectuated by way of a cellular communication system are generally effectuated pursuant to a subscription for service in the communication system.
In a cellular communication system, the communication stations form radio transceivers capable both of sending and receiving signals upon communication channels defined upon the radio link extending therebetween. Radio transceivers of a network part of the cellular communication system are referred to as base transceiver stations (BTSs), and radio transceivers carried by subscribers to the system and used by the subscribers to communicate telephonically in the communication system are referred to as mobile stations.
The communication channels upon which data is communicated between a base transceiver station and a mobile station are non-ideal. Distortion is introduced upon the data during its transmission. The distortion is caused, for example, by fading conditions exhibited by the communication channel. If the distortion cannot be adequately compensated for when the data is received at a receiving station, the informational content of the data cannot adequately be recovered.
Various mechanisms are used to reduce the effects of the distortion. For instance, the data that is to be communicated is encoded prior to its communication. Encoding of the data increases its redundancy. When a portion of the data is distorted, a redundant portion of the distorted data might not be so distorted as to prevent its recovery. Creation of physical diversity is sometimes also utilized in an effort to overcome the distortion introduced upon the data during its communication upon the communication channel. Physical diversity is created, for example, through the use of two or more spaced-apart, transmit antennas at which the data is transduced for communication upon the communication channel by way of separate paths thereon.
Interleaving of the data, usually subsequent to encoding thereof, is sometimes also utilized to overcome the effects of distortion. By interleaving the data, distortion affecting a portion of transmitted data is less likely to distort a segment of data that, once deinterleaved at a receiving station, prevents recovery of the informational content thereof. Conventionally, when interleaving is performed, the interleaving is performed upon modulated and rotated symbols of the data. In a trellis-coded modulation (TCM) communication scheme, modulated and rotated symbols are formed of both real and imaginary component parts. Coordinate interleaving of these coordinate parts of the symbols can also be performed. And, increasing the modulation coding of the data that is to be communicated also is used to overcome the distortion introduced upon the data during its communication upon a non-ideal channel.
Generally, a goal is to maximize the coding gain of the data that is to be communicated, best to overcome the effects of distortion while minimizing the computational complexity required to provide the coding gain.
Any manner by which to maintain a selected level of coding gain while requiring only a reduced computational complexity of operations to provide such coding gain would be advantageous.
It is in light of this background information related to the communication of data in a communication system that the significant improvements of the present invention have evolved.